ODLIS — Online Dictionary for Library and Information Science by Joan M. Reitz Now available in print! Order a copy of the hardcover or paperback from Libraries Unlimited.

D

DACS

See: Describing Archives: A Content Standard.

daemon

The Greek word for "guardian spirit." In computing, an auxiliary systems program initiated at startup and executed in the background that performs a specific task when needed, for example, running a scheduler to start another process automatically at a pre-established time, checking incoming e-mail messages for addresses that cannot be found, or notifying the sender that a message could not be delivered. Pronounced "demon."

dagger (†)

In printing, a character in the shape of a vertical stroke crossed above its midpoint, used in text as a second-order reference mark following use of the asterisk (*). When it appears before a personal name in the English language, the dagger indicates that the individual is deceased. Also called an obelisk or long cross. See also: double dagger.

daguerreotype

Historically, the first photographic process that actually worked, producing a positive image directly on a highly polished, silvered copper plate sensitized with iodide vapor. By exposing the plate to light in a camera obscura, a laterally reversed latent image was captured in the photosensitive layer of silver iodide that could be developed with the application of mercury vapor. Made public in 1839, the process was named after its French inventor, the painter of dioramas, Louis Jacques Mande Daguerre, who relied heavily on earlier experiments by Joseph Nicephore Niepce. Daguerre taught the process to Samuel B. Morse (of Morse code) in Paris in 1839, who subsequently taught it to paying students in the United States.

Although the daguerreotype was capable of capturing fine detail, the highly polished surface had a mirror effect when viewed at an oblique angle and was easily scratched and tarnished. For this reason, daguerreotypes were typically protected under a metal mat, covered by a plate of glass, and enclosed in a case (click here to see examples). Early examples are valued by collectors because each is unique, not having been made from a negative. For other examples, see the online exhibitions Secrets of the Dark Chamber (Smithsonian American Art Museum) and The Dawn of Photography: French Daguerreotypes, 1839-1855 (Metropolitan Museum of Art), or try the Daguerreian Society. Also spelled daguerrotype. Compare with calotype. See also: ambrotype, composite daguerreotype, and tintype.

daguerrotype

See: daguerreotype.

DAI

See: Dissertation Abstracts International.

dailies

See: rushes.

daily

Issued on a daily basis, with the possible exception of Sundays. Also refers to a serial issued daily, especially a newspaper.

DAM

See: digital asset management.

damaged

An item returned to the library in such poor condition that it cannot be placed back on the shelf for circulation, for example, a water-soaked or pet-chewed book. The borrower is normally charged the cost of repair or replacement. New items received from the shipper in damaged condition are returned by the library to the seller for credit or replacement. Click here to see a copy of the first printed edition of Marsilio of Padua's The Defender of Peace damaged in the English bombardment of Copenhagen in 1807 (Royal Library of Denmark) and here to learn about the most common types of damage, courtesy of the Heritage Collections Council, Australia. See also: defacement.

dampstain

A visible stain, often in a shade of gray or tan, found on the covers or leaves of a book, caused by exposure to moisture, water, or some other liquid (see this example). When minimal, it is tolerated by collectors in the absence of mildew in very old, scarce books, but its presence lowers the monetary value of the item.

Dana, John Cotton (1856-1929)

A public librarian for over 40 years, John Cotton Dana began his career in 1889 as head of the Denver Public Library, moved to the City Library of Springfield in 1898, and ended his career at the Free Public Library in Newark, New Jersey. An early leader in the library profession, he served as president of the American Library Association (ALA) from 1895 to 1896, as a member of its council from 1896 to 1902, and as president of the Special Libraries Association from 1909 to 1910, an organization he helped to establish. His philosophical approach to librarianship is best expressed in his book Suggestions, published in 1921 by F.W. Faxon. Click here to learn more about John Cotton Dana, courtesy of the Rutgers University Libraries. See also: John Cotton Dana Award.

dandy roll

The cylinder that exerts pressure in mechanized papermaking, smoothing the surface and creating designs such as the watermark, countermark, and the lines characteristic of laid and wove paper (see this example).

Dartmouth Medal

A literary award presented annually since 1974 by the Reference and User Services Association (RUSA), a division of the American Library Association (ALA), to the most outstanding reference work published during the preceding calendar year. Click here to see a list of Dartmouth Medal recipients.

dash

A short length of horizontal rule used for punctuation, to separate text, and for decorative effect. In printing, dashes vary in length from the three-em (longest) to the hyphen (shortest). In typing, a dash is made by striking the hyphen key twice in succession (--). In descriptive cataloging, the dash is preceded and followed by a space, but when it is used in subject headings to indicate subdivision, no spaces are included (example: Libraries--Aims and objectives).

dashed-on entry

A pre-AACR2 convention of indicating accompanying material and additional versions on the catalog entry for the main item, a practice that economized on the number of catalog cards needed for items sharing basic bibliographic description. This type of entry was eliminated in AACR2, reflecting a shift from card catalogs to MARC-based electronic catalogs. Synonymous with dash entry and dash on entry.

dash entry

See: dashed-on entry.

dash on entry

See: dashed-on entry.

dasymetric map

A thematic map similar to a choropleth map in the use of areal symbols (tint, shading, hatching, etc.) to represent quantitative data, but instead of mapping the data to areas that correspond to administrative or enumeration units, ancillary variables are employed to change the boundaries of the areas to better represent the areal distribution of classes of data. Click here to see an example showing the distribution of population density in Greece in 1973, courtesy of the Perry-Castañeda Library (to enlarge click on lower right corner of image).

data

The plural of the Latin word datum, meaning "what is given," often used as a singular collective noun. Facts, figures, or instructions presented in a form that can be comprehended, interpreted, and communicated by a human being or processed by a computer. Compare with information and knowledge. See also: data bank, database, data set, and metadata.

data bank

Sometimes used synonymously with database, the term applies more specifically to a collection of nonbibliographic data, usually numeric (example: Global Soil Moisture Data Bank available online from the Department of Environmental Studies at Rutgers University). Large data banks containing information about individuals (social security numbers, credit history, health records, etc.) have become the subject of controversy as the rapid development of high-speed information technology poses new threats to personal privacy.

database

A large, regularly updated file of digitized information (bibliographic records, abstracts, full-text documents, directory entries, images, statistics, etc.) related to a specific subject or field, consisting of records of uniform format organized for ease and speed of search and retrieval and managed with the aid of database management system (DBMS) software. Content is created by the database producer (for example, the American Psychological Association), which usually publishes a print version (Psychological Abstracts) and leases the content to one or more database vendors (EBSCO, OCLC, etc.) that provide electronic access to the data after it has been converted to machine-readable form (PsycINFO), usually on CD-ROM or online via the Internet, using proprietary search software.

Most databases used in libraries are catalogs, periodical indexes, abstracting services, and full-text reference resources leased annually under licensing agreements that limit access to registered borrowers and library staff. Abbreviated db. Compare with data bank. See also: archival database, bibliographic database, embedded database, metadatabase, and niche database.

database management system (DBMS)

A computer application designed to control the storage, retrieval, security, integrity, and reporting of data in the form of uniform records organized in a large searchable file called a database. The range of available DBMS software extends from simple systems intended for personal computers to highly complex systems designed to run on mainframes.

data compression

The algorithmic re-creation of a data file to reduce the amount of memory required for storage. Exchange of compressed data requires less transmission time but more computation time to restore it to its original form for processing. In digital imaging, a number of compression methods are used, including JPEG, GIF, and LZW. Compression algorithms are classified as lossless or lossy, depending on whether data is lost in compression. Click here to learn more about file compression, courtesy of HowStuffWorks.

data conversion

The process of translating data from one form to another, usually from human-readable to machine-readable format (or vice versa), from one file type to another, or from one recording medium to another, for example, from film to videotape or videodisc using a telecine.

data dictionary

A set of data descriptions documenting the fields (columns) in the tables of a database system. A data dictionary may describe the data type and other physical characteristics of fields, enumerate allowed values, and specify appropriate usage.

Data Documentation Initiative (DDI)

A project of the social science community to develop a standardized XML markup and representation for codebooks, the primary metadata describing social science data sets. Click here to learn more about the DDI.

data element

See: element.

data logger

An electronic instrument designed to record measurements (temperature, relative humidity, light intensity, on/off, open/closed, voltage, pressure, etc.) over time. Typically they are small, battery-powered devices equipped with a microprocessor, data storage, and sensor. Most utilize turn-key software installed on a personal computer to initiate the logger and view the collected data. They are used for a wide variety of applications, especially in remote areas for the convenience of automatic recording. Libraries and archives use them to monitor environmental variables that affect the condition of collections.

data processing

The systematic performance of a single operation or sequence of operations by one or more central processing units on data converted to machine-readable format to achieve the result for which the computer program that controls the processing was written, for example, the compilation of circulation statistics from records of circulation transactions occurring in a library over a given period of time.

data set

A logically meaningful collection or grouping of similar or related data, usually assembled as a matter of record or for research, for example, the American FactFinder Data Sets provided online by the U.S. Census Bureau or the National Elevation Dataset available from the U.S. Geological Survey. Also spelled dataset. See also: social science data set.

data stick

See: USB flash drive.

data strip

A long, narrow band across the back of a card, coated with a magnetic medium (usually dark in color) bearing encoded digital information that can be read by a specially-designed device (see this example). Commonly used to record the account number on plastic credit and debit cards, data strips are also used on some library cards to record patron ID or card number. Synonymous with magnetic strip, magnetic stripe, and magstripe.

date

A particular point in time, usually with reference to a specific event or happening. Date usually means a specific day of the month, but is sometimes given as month and year (e.g., May 1861), or merely the year, as in the publication date of a book or the release date of a motion picture or sound recording. A date range is normally given as the beginning date and ending date, separated by a hyphen (1860-1864), as in inclusive dates and bulk dates. References to increments smaller than a day (hour, minute, second) are typically referred to as time. See also: false date.

date due slip

A card or slip of paper inserted in an item charged from a library collection or a small printed form attached to the inside of the front or back cover or to one of the free endpapers, on which is stamped the date the item is due back in the library (see this example). The paper on which they are printed should be acid-free. Date due slips are sometimes removed by borrowers in an attempt to avoid overdue fines, but the advent of automated circulation systems has nixed this strategy. Synonymous with charge slip.

date line

The line printed at the beginning of a story in a newspaper or article published in a newsmagazine, indicating the date and place of origin of news that is not local. See also: byline.

date range

An interval of time marked by a beginning date and an ending date. Some online catalogs and bibliographic databases allow the user to limit a search to a specific range of publication dates. A year followed by a hyphen (1946- ) limits retrieval to information published in the year specified or any succeeding year, a year preceded by a hyphen ( -1945) limits retrieval to sources published up to and including the year specified, and a year followed by a hyphen and a subsequent year (1939-1945) limits retrieval to sources published in those or any intervening years. See also: bulk dates and inclusive dates.

datum

In cartography, a set of accurately surveyed horizontal control points that define the shape of the earth as an ellipsoid, forming the basis for a two-dimensional system of geographic coordinates, for example, the North American Datum of 1983, a readjustment of a pre-existing horizontal control network established and maintained by the National Geodetic Survey. NAD 83 is composed of over 250,000 monumented control stations across the continental United States, interconnected by survey observations. The stations are used by surveyors operating at the federal, state, county, and city levels to reference boundaries, provide control in mapping and charting, and for other purposes. Sea level is the vertical datum used to calculate elevation, but because the level of the sea surface is determined by gravity (and the earth's rotation), which varies according to differences in the density of the earth's core, sea surface topography varies significantly. To assure accuracy, geographers have developed sophisticated techniques for measuring mean sea level. To learn more, see Peter H. Dana's Geodetic Datum Overview. Plural: datums.

In a more general sense, any numeric value or geometric surface, line, or point that serves as a base or reference for other quantities (SARBC Map and Compass Glossary). In the broadest sense, a thing that is given or known to be factual, upon which a reasoned argument or calculation is based. Also, an assumption or premiss from which inferences are subsequently made (OED).

daybook

In bookkeeping, a record of the details of each day's receipts and expenditures in chronological order of occurrence (usually entered in a bound volume), as distinct from a ledger in which financial transactions are recorded by account, as credits and debits. Click here to see a 19th-century medical example (University of Virginia Health Sciences Library) and here to see an example kept by an artist. Also spelled day book. Synonymous with waste book.

Also, a calendar, in print or electronic format, of forthcoming events (celebrations, performances, meetings, workshops, seminars, etc.). Also used in reference to a calendar designed as a personal organizer. Click here to see the daybook of President John F. Kennedy's personal secretary, Evelyn Lincoln (JFK Presidential Library & Museum).

DBMS

See: database management system.

DBV

See: Deutscher Bibliotheksverband e.V.

DCMI

See: Dublin Core.

DDC

See: Dewey Decimal Classification.

DDI

See: Data Documentation Initiative.

DDS

See: document delivery service.

deaccession

The process of deleting from an accession record documents and other materials that are to be removed from a library collection. Also refers to any item so removed. The opposite of accession.

In archives, the process of removing records or documents from official custody, undertaken after careful consideration, usually as the result of a decision to transfer the material to another custodian or because the legal owner desires its return or the material is found upon reappraisal to be of doubtful authenticity or inappropriate for the collection. Synonymous with permanent withdrawal.

deacidification

A general term for a variety of costly preservation processes that chemically reduce the acid content of paper documents to a pH of 7.0 (neutral) or higher, usually undertaken at a professional conservation center to prevent further deterioration. An alkaline buffer may be deposited in the process of deacidification to neutralize any acids that may develop in the future. Brittleness is not reversed by deacidification.

In aqueous deacidification, water is used as the solvent carrier of the alkaline agent; in nonaqueous deacidification, organic solvents are used as the carrier. In vapor phase deacidification, documents and the pages of volumes are interleaved with treated sheets that emit an alkaline vapor, a method now rarely used because it produces toxic vapors and does not leave an alkaline reserve (Richard Pearce-Moses, A Glossary of Archival and Records Terminology). Mass deacidification is the shipment of a quantity of documents to a central location for processing, usually in small batches rather than individually. Click here to see in situ deacidification at the Bodleian Library (University of Oxford) and here to see mass deacidification at the Northwestern University Library.

Dead Sea Scrolls

Ancient papyrus and parchment manuscripts stored inside large pottery jars, discovered in caves in the Judean Desert in 1947 by Bedouin shepherds. Radiocarbon dating has established that the scrolls, and the Essene community at wadi Quram with which they are believed to be associated, date from 250 B.C. to A.D. 65. Written in Aramaic, the scrolls comprise about 800 documents of which most are in fragmentary condition. They include the oldest extant text of the Old Testament. The tedious work of piecing them together has taken decades. The scrolls are in the possession of the Israel Antiquities Authority in Jerusalem, where they are being prepared for publication by Oxford University Press in what will eventually be a thirty-five volume work entitled Discoveries in the Judaean Desert (see Dead Sea Scrolls Foundation). The Library of Congress provides the online exhibit Scrolls from the Dead Sea. Examples can also be seen in the Schøyen Collection (Oslo and London) and Treasures from the World's Great Libraries, courtesy of the Israel Antiquities Authority and the National Library of Australia.

dealer

An individual or commercial company in the business of buying and selling new and used books to libraries, collectors, and other booksellers. Although the term is sometimes used synonymously with vendor or jobber, it is usually reserved for specialists who deal in out of print titles, rare books, periodical back issues, etc. See also: antiquarian bookseller.

dean

The position title used in some institutions for the chief executive of a large academic library system in which the professional staff have faculty status and the chief executive also serves as head of the library faculty. The official title is usually "Dean of Library Services" or "Dean of Information Services." Compare in this sense with library director. Also, the title designating the chief academic and administrative officer of most library and information studies programs in the United States. A dean normally serves at the discretion of the president of the institution.

deblooping

See: bloop.

decal

An image (often a logo) made on paper specially treated to allow the image to be transferred to another surface, such as glass, plastic, or metal, usually by wetting the paper, then placing it face down against the other surface and peeling away the backing sheet. In libraries, decals are collected as a form of ephemera.

decennial

Issued every 10 years (example: U.S. Census). Also refers to a serial publication issued every 10 years. See also: annual, biennial, triennial, quadrennial, quinquennial, sexennial, and septennial.

decimal point

The period used in the numeric portion of Library of Congress Classification notation (example: DK 265.9) and following the third digit of a class number in Dewey Decimal Classification (947.084) to indicate that succeeding digits are to be treated as a decimal fraction.

Decision Document

The official document sent to the dean of a library and information studies program and to the institution?s chief executive officer conveying the accreditation action taken by the Committee on Accreditation (COA) of the American Library Association (ALA) as the result of a two-year comprehensive review to verify that the program conforms to the ALA's Standards for Accreditation of Master's Programs in Library and Information Studies (1992). If accreditation is withdrawn or denied, the program or institution may appeal the decision. See also: special report.

deckle edges

The uneven or feathered edge of a sheet of handmade paper, created by the flow of liquefied fibrous stock between the frame (deckle) and sieve of the mould used in manufacture. The same effect is achieved in machine-made paper by exposing the edge to a jet of air or water. In quality bookbinding, deckle edges are considered tasteful, but since books tend to collect dust when stored on an open shelf, and rough edges are difficult to clean, the feature is not practical. Click here to see an example and here to compare deckle edges with other edge treatments. Compare with cut edges.

declassified

A document no longer protected against unauthorized disclosure because the security classification assigned to maintain confidentiality has been officially changed or canceled. Examples can be seen at the Web site maintained by The National Security Archive, an independent non-governmental research institute and library located at George Washington University in Washington, D.C. The opposite of classified. See also: declassification.

declassification

The process of removing the security classification from materials restricted by a government for reasons of national security, to make the information contained in them accessible to individuals without security clearance. In a declassification project, an entire category or group of documents is evaluated for possible declassification (see this example at the Gerald R. Ford Presidential Library and this project at the U.S. Department of State). Compare with downgrade. See also: reclassification.

declination

Angular distance north or south from the celestial equator measured on a great circle (meridian) passing through the celestial poles, corresponding to terrestrial latitude. Magnetic declination (sometimes called magnetic variation or compass variation) is the angle between magnetic (compass) north, determined by the earth's magnetic field, and true north for a given location. The actual location of the magnetic north pole changes over time due to shifts in the earth's magnetic field, but its current location is northwest of Hudson's Bay in northern Canada, about 450 miles from the geographic north pole. The line of zero declination runs from magnetic north through Lake Superior and the western panhandle of Florida. Along this line, true north is the same as magnetic north. Magnetic declination is designated positive when the angle measured is east of true north and negative when west of true north. The orientation of maps and charts is based on geographic north because it remains constant. On some maps, a declination diagram or note, usually located near the scale, indicates the angular relationships of true north, magnetic north, and grid north (click here to see an example). Click here to see the concept illustrated and here to learn more about declination.

decomposition vent

An opening in a storage chamber made to allow the escape of gases (usually toxic or flammable) produced in the deterioration of the stored material. For example, the National Fire Protection Association (NFPA) has established a standard requirement for decomposition vents in chambers used to store chemically unstable cellulose nitrate film.

decorated edges

See: edge decoration.

decorated initial

An initial letter in an illuminated manuscript or early printed book embellished in an abstract, nonrepresentational style, rather than with foliate, zoomorphic, and/or anthropomorphic motifs or pictorial elements. Click here to see a fine penwork example in a 15th-century Spanish antiphonal (Dartmouth College Library, MS 002103) and here see a large painted example in a 14th-century Italian Bible (Cary Collection, Rochester Institute of Technology). Within a medieval manuscript, there is usually a hierarchy of initials of varying size and complexity to designate the beginning of sections, chapters, paragraphs, and other breaks in the text (see this example, courtesy of the British Library, Arundel 155).

decorated map

An old map embellished with purely ornamental motifs (foliage, geometric designs, etc.) or drawings of human figures, animals, or small landscapes that may be related to the map's content, but are not used to represent data. A coat of arms signified land ownership. Map decoration usually appears around the edges, in the corners, over the oceans, or in the form of an elaborate cartouche. Click here to see a heavily decorated 17th-century world map and here to see an 18th-century example depicting the Salzburg province of Austria (Library of Congress) and here for an elaborate 19th-century French example (George Glazer Gallery). Click here to see a 20th-century manuscript chart of the Far East with decoration superimposed on the mapped area (National Maritime Museum). Compare with illustrated map and pictorial map.

decorated paper

Fine paper hand-printed in Germany, France, and Italy from patterns carved into woodblocks, used in luxury bookbinding from the 18th century on for doublures and flyleaves. Dutch gilt was a multicolored floral pattern blocked in gold, shipped from Germany to the Netherlands for re-export. Click here to see a sample of brocade paper made in the 18th-century (Koninklijke Bibliotheek) and here to see decorated paper used as doublure and flyleaf in a 19th-century deluxe binding (University of North Texas Libraries). To see examples of decorated paper used as a covering material, try a keywords search on the term "decorated paper" in the British Library's Database of Bookbindings. Click here to see a late 19th-century German recipe book for making decorated paper (Koninklijke Bibliotheek) and here to see a collection of decorated papers at the Folger Shakespeare Library. See also: marbling, paste paper binding, and silhouette paper.

decorated spine

See: spine decoration.

decretals

A book containing a collection of letters written to transmit papal decrees, usually concerning canon law, often made in response to a specific appeal. Michelle Brown notes in Understanding Illuminated Manuscripts (Getty Museum/British Library, 1994) that copies of decretals used by ecclesiastical and civil officials, and for purposes of study at universities, often included commentaries written as glosses alongside the text and sometimes decoration (miniatures, bas-de-page scenes, grotesques, etc.). Click here to view an illuminated copy of the decretals of Pope Gregory IX (Bodleian Library, University of Oxford, MS Lat. th.b.4), and here to page through decretals compiled by Gratian in the 12th century (Getty Museum, MS Ludwig XIV 2).

dedicated

In computing and communications, a device or channel reserved for a specific use. In libraries, dedicated servers are used to run the online catalog and to provide access to the library's Web site. See also: dedicated line.

dedicated line

A direct pathway to the Internet or some other computer network via a separate telecommunications channel not shared with multiple users as in dial-up access but available around the clock to a specific user or group of users for a designated purpose. When accessed through a common carrier, the channel is called a leased line.

dedication

A brief note in which the creator of a work addresses it to one or more persons, usually a colleague, mentor, or family member, as a sign of honor, appreciation, or affection. In books, the author's dedication appears in the front matter, usually printed on the recto of the leaf following the title page. Click here to see the handwritten dedication by 17th-century composer Michael Praetorius of his motets to Christian IV of Denmark (Royal Library of Denmark) and here to see the dedication by William Davenant of a printed edition of his play The Just Italian to the Earl of Dorset (Columbia Rare Book & Manuscript Library). Compare with acknowledgments.

dedication copy

A copy of a book or other work inscribed by the author, editor, or illustrator to the person or persons to whom the work is dedicated. In the antiquarian book trade, a dedication copy may be of substantially greater value than a copy with no inscription and is considered one of the most collectible presentation copies of an edition. Click here to see the hand-colored copy of Le Jardin de Plaisance & Fleur de Rhetorique, an anthology of poems edited by Anthoine Vérard, dedicated to the French King in about 1500 (Royal Library of Denmark).

dedication miniature

See: presentation miniature.

deduping

Removal of all but one occurrence of a bibliographic record from a file of machine-readable records, one of the initial steps in processing a MARC database. Deduping is a batch process that prevents confusion in the minds of users, conserves computer storage, and allows reliable usage statistics to be collected. Duplicate records are not uncommon because the "cancel holdings" command in OCLC software does not delete a record from the library's OCLC tapes. Synonymous with duplicate removal and duplicate resolution.

deed

A legal document, written or printed, stating a contract, agreement, or transfer of property, especially real property, usually signed by the parties. As a legal instrument, deed is distinguished from title, which is a legal right. Although title is sometimes used synonymously with deed, the latter is normally used only in the narrower sense of the actual instrument. Click here to see a 16th-century English title deed written on parchment and here to see an 18th-century American example signed by Daniel Boone, courtesy of The Lilly Library at Indiana University. The State Library of South Australia provides an image of the Deed of Settlement of the South Australian Company (1856). See also: charter.

deed of gift

A signed document stating the terms of agreement under which legal title to real, personal, or intellectual property, such as a gift of materials to a library or archives, is transferred, voluntarily and without recompense, by the donor to the recipient institution, with or without conditions specifying access, use, preservation, etc.

deep linking

A link made from a Web document to the interior of another Web site, bypassing the second site's homepage, usually without any indication that a shortcut has been taken. Deep linking raises digital rights issues, particularly for commercial entities that derive income from advertising on their main page. Likelihood of litigation depends on the type of site involved and the nature of the content accessed. Libraries should seek permission before deep linking from their Web pages.

deep web

Publicly accessible information available via the World Wide Web but not retrievable using search engines that rely on crawlers or spiders, for example, data in file formats such as PDF, database content accessible only by query, information contained in frames, etc. The number of documents available in the deep web is estimated to be 400-500 times greater than the amount of content retrievable via conventional search engines (the "surface Web"), with over half of the "hidden" content residing in topic-specific searchable databases. CompletePlanet and direct search are examples of Internet services specifically designed to provide access to information buried deep in the Web. See also OAIster and Wikipedia. Click here to learn more about the deep content, courtesy of BrightPlanet. Synonymous with invisible web.

The term is also used for password-protected Web content available only to authorized users (members, subscribers, etc.).

deerskin

A soft leather made from the skin of a deer. Its use in bookbinding is rare (see this example, courtesy of Washington State University). On medieval bindings, it was sometimes applied as an outer layer to protect the inner covering material. Click here to see a 14th-century example (Koninklijke Bibliotheek).

defacement

Damage to library materials by deliberate intent, rather than accident or neglect, including but not limited to cutting or tearing of pages and covers, underlining or highlighting portions of text, and writing or doodling in margins (see these examples, courtesy of the University of Michigan Libraries). Compare with vandalism.

de facto standard

A criterion or consistent manner of doing something, so established in practice that adherence is widespread if not universal, although its status has never been formalized. Such standards are often the result of one method or product becoming so dominant in the market place that its influence is comparable to that of a formally established standard. Examples include the Kermit communication protocol in computing and the compact cassette in sound recording. Compare with de jure standard. See also: best practices.

default

A value, option, or setting automatically selected in a hardware or software system in the absence of specific instructions from the user. The default setting may be displayed on the data entry screen to allow the user to see what action will be taken if no input is provided.

definition

One meaning of a word expressed clearly and concisely. Because some words have more than one meaning, a word may have more than one definition. In lexicography, a word or phrase is defined by first specifying the class (genus) to which its referent belongs, then indicating the characteristics that distinguish the referent from others of the same class. Definitions are provided in dictionaries and glossaries and are also included in some concordances and thesauri. In most dictionaries, the modern definition of a word is given first and the oldest last, but there are notable exceptions to this rule. Abbreviated def. See also: headword.

Also refers to the distinctness of a printed or photographic image.

definitive edition

An edition of the complete text of an author's work or works, usually edited and published after the individual's death in a form considered final and authoritative, often including the critical apparatus documenting variations in the work and explaining the editor's choice of version. Also refers to the text of an anonymous work considered by scholars or other experts, upon close examination, to be closest to the original version. Compare with authorized edition. See also: critical edition and variant edition.

degaussing

The process of permanently removing data recorded on a magnetic medium (hard disk, floppy disk, magnetic tape, etc.) by neutralizing the magnetic signals in which the information is encoded, accomplished by subjecting the medium to a magnetic field generated by a device called a degausser, named after the German scientist Carl Friedrich Gauss, who contributed significantly to many fields in mathematics and science, including magnetism. Click here to learn more about degaussing, courtesy of Wikipedia. Synonymous with erasure.

degressive bibliography

A term introduced by Bodleian librarian Falconer Madan in the early 20th century for his habit of varying the amount of detail in the bibliographic description of a work based on the period of time in which the work was published or on the importance of the publication. Under this principle, the first edition of a work might merit more detailed description than a subsequent edition or reprinting.

dehumidify

See: humidity.

de jure standard

A criterion or consistent manner of doing something, formally established in a deliberative process involving one or more professional organizations or industry groups, a government body, or a recognized standard-setting organization (see International Organization for Standardization). It is not unusual for the development process to require negotiations in which a consensus is reached among parties with competing interests, especially when the financial stakes are high. Compliance is not compulsory, but may be made so by national regulations. The Z39.50 client-server protocol and Ethernet are examples of de jure standards. Compare with de facto standard.

delamination

The process of removing layers of thin, clear plastic film from a sheet previously subjected to the process of lamination. Because laminate adheres to the surface to which it is applied, delamination often causes irreversible damage to the laminated document. For this reason, encapsulation is preferred by preservationists.

Also refers to the process by which the components of a sheet of writing or binding material composed of multiple layers adhered one to another come apart, usually from heavy use, as in a sheet or roll of papyrus (see this example, courtesy of the Schøyen Collection, MS 1644). In nonprint media composed of multiple layers (compact discs, DVDs, photographic film, magnetic tape, etc.), delamination occurs when the binding mechanism fails.

delayed publication

A book or periodical not issued on schedule, usually due to delays in production. Also refers to new information not published in a timely manner, for whatever reason.

delete

To remove, erase, or omit a character, word, or passage from a text or document. In computing, to erase a character, word, passage, or entire file from memory, usually by pressing the "Backspace" key on a keyboard or by highlighting text and pressing the "Delete" key or selecting the "Delete" option from a menu or toolbar. Most software systems allow the user to "Undo" a deletion while the application remains open.

delimiter

In a general sense, any character or sequence of characters used in an electronic database to separate discrete elements of data within a field (or fields) of a record. In the MARC record, a character used as the first character of a two-character subfield code to indicate the beginning of a subfield, separating one data element from another within the field. The display representation of the MARC subfield delimiter is not standardized. In OCLC it is represented by a double dagger (‡) and in Library of Congress cataloging by the dollar sign ($).

delinquent borrower

A borrower who fails to return items charged from the library collection within the allowed time or who fails to pay fines or for lost items. Most libraries impose sanctions on borrowers who do not meet their obligations. Such a person may be barred from checking out additional materials. Public libraries may eventually send the borrower's account to a collection agency. Some academic institutions withhold the diploma until library fines are paid. Compare with problem patron.

delivery time

The amount of time it takes to receive materials ordered from a vendor, usually 1-3 months. Delivery time varies with type of material, amount of information provided by the library, and specific vendor. From book jobbers that maintain adequate inventories, libraries can expect receipt of an initial shipment containing 75-80 percent of materials ordered within 2 weeks of date of order. Vendors used by academic libraries typically deliver within 6-8 weeks. As a general rule, materials recently published by major houses are delivered faster than older publications issued by smaller companies. Titles published abroad may take longer because international shipping requires more time than domestic shipping. A service charge is usually added for a rush order. Some vendors automatically cancel orders that remain unfilled after 6 months, but others leave them open indefinitely or expect the library to specify the action to be taken. See also: claim.

deluxe binding

French for "of elegance." A binding of very fine quality, usually covered in leather or fine cloth stamped or tooled in gold, sometimes with gilt edges and doublures or endpapers of marbled or decorated paper. Click here and here to see examples by 16th-century Saxon binders (Dresden: Treasures from the Saxon State Library) and here to see an 18th-century example in morocco by the First Stadholders' Bindery in The Hague (Koninklijke Bibliotheek) Click here to see the inside of a 19th-century French deluxe binding with tooled leather doublures and marbled endpapers (Princeton University Library). Also spelled de luxe binding. Compare with fine binding. See also: deluxe edition.

deluxe edition

An edition printed on better quality paper than the standard trade edition, sometimes from specially cast type, usually bound in leather or some other material of fine quality (see this example). Deluxe editions may also be larger in size, more lavishly illustrated, and published in limited edition. Also spelled de luxe edition. Synonymous with fine edition. See also: deluxe binding.

DEM

See: digital elevation model.

demand

The number of people who need or request a product or service. In libraries, high-demand items may be ordered in multiple copies or placed on reserve to ensure access. In public libraries, low-demand items in the circulating collection may be candidates for weeding. Demand for library services usually peaks at different times during the day, week, month, and year. Transaction logs can be helpful in tracking and anticipating patterns of usage.

demand publishing

See: on-demand publishing.

DEMCO

A commercial company that provides furniture, equipment, and supplies for the library, school, office, and home. DEMCO also provides periodical subscription services. Click here to connect to the DEMCO homepage. See also: Brodart, Gaylord, and Highsmith.

demolding

The process of removing mold and mold spores from a book or library collection to prevent an infestation from spreading (heavily infested items should be discarded whenever possible). When done professionally, affected materials are first desiccant air dried to remove excess moisture, then treated with antimicrobial cleaning solutions and sanitizers supplied by companies such as Microban. Mold in library carpet and furniture can be eliminated by using a fungicidal disinfectant. On hard surfaces, such as shelving, a mild bleach solution can be used as a wipe-down agent. For more information, see the Oxford University Library's guidelines on Collection Care & Conservation. Also spelled demoulding.

density

In typography, the number of characters filling a given space, a variable affecting legibility of type. In photography, the degree of opacity of a developed photosensitive medium, such as film. In printing and photography, the density of an image is measured by an instrument called a densitometer.

In computing, the amount of data, usually measured in bits or bytes, that can be stored in or on a given storage medium, such as a memory chip or portable disk. A floppy disk can be single-density, double-density, high-density, or extra-high-density. A disk drive designed to support the specific density level is required.

In photography, the relative difference between the lightest and darkest portions of the image, as measured by an instrument called a densitometer. Also, the relative amount (opacity) of the material forming the image on exposed photographic film (usually silver oxide) which affects the amount of light transmitted through the negative.

dentelle binding

A style of 18th-century leather binding in which the covers are decorated on the outer and/or inner surface with broad, full borders gold-tooled in a finely detailed pattern resembling lacework. Click here to view a blankbook gold-tooled in dentelle style (Koninklijke Bibliotheek) and here to see dentelle decoration of the turn-ins on a deluxe binding (University of Pittsburgh Libraries). To see more examples, try a keyword search on the term in the British Library's Database of Bookbindings.

departmental library

A type of academic library that serves the information and research needs of the faculty members of a department within an institution of higher learning, usually a large university. Departmental libraries are also used by students enrolled in courses in the discipline(s) taught by the department, especially graduate students. If acquisitions are funded through the department, selection is usually the responsibility of the teaching faculty in collaboration with the departmental librarian.

dependent work

In library cataloging, a work that is contingent in some way on a previously published work by another author. The category includes abridgments, arrangements, commentaries, continuations, dramatizations, sequels, revised editions, and supplements. Synonymous with related work. Compare with derivative work.

deposit

Any addition to archival holdings, usually a transfer of materials from some other location or agency, but the term also applies to materials on loan for a period of fixed or indefinite duration. The depositor usually retains legal ownership and responsibility, except in the case of gifts. See also: deposit copy and depository library.

Also refers to a fixed fee deposited in the account of a person who is not a member of the library?s regular clientele but who wishes to receive borrowing privileges, usually refundable upon return of the borrowed materials or when the borrower wishes to terminate the agreement. Not all libraries have such a policy.

deposit account

In acquisitions, a vendor prepayment account into which the customer deposits a substantial sum, against which orders are subsequently charged. When the balance in the account reaches zero, an additional amount must be deposited for fulfillment to continue. In return, the library receives a financial incentive in the form of an annual credit based on an agreed rate, a larger than normal discount on purchases, or interest paid on the balance in the account. A library's funding authority usually dictates the feasibility of this type of account (some institutions prefer to earn interest on the money rather than allow the library to expand its purchasing power). There is risk to the customer, should the vendor go out of business before the end of the deposit period.

deposit copy

A copy of a new publication sent without charge to a copyright depository or other designated library by the author or publisher in compliance with national copyright law. In the United States, the deposit copy is sent with the completed copyright application form and copyright fee to the U.S. Copyright Office of the Library of Congress in Washington, D.C. Synonymous with statutory copy.

deposition

Out-of-court testimony given under oath, often in an attorney's office, by the defendant or plaintiff, a witness to the event, or an expert witness, and transcribed by a court reporter for use in pretrial discovery (investigation) or in court, as though the witness were present and testifying (see this historic example). If a written transcript is requested, the deponent normally receives a copy. Depositions are increasingly recorded on videotape. At trial, deposition testimony may be used to impeach a witness who makes contradictory statements or to refresh the memory of a witness. If a deposed witness is unavailable at time of trial (for example, in a case of serious illness or death), the deposition may be read to the jury in place of in-person testimony. Also refers to the process of taking such testimony.

depository library

A library legally designated to receive without charge all or a portion of the government documents provided by the U.S. Government Printing Office (GPO) and other federal agencies to the Superintendent of Documents for distribution through the Federal Depository Library Program (FDLP), having made a legal commitment to comply with federal regulations concerning maintenance and accessibility. Some federal depositories also collect publications issued by state government agencies. A regional depository library receives and retains permanently at least one copy of all the documents distributed through the FDLP, but a selective depository library receives only a percentage of the available publications and is required to retain them for a minimum of 5 years. Depository libraries are required to complete a self-study and/or undergo inspection at intervals of 6-7 years to assure compliance with FDLP rules and regulations. Click here to connect to the GPO Access Federal Depository Library locator service. Compare with repository. See also: basic collection, Depository Library Council, and depository library number.

Depository Library Council (DLC)

Formally established in 1972, the Depository Library Council is appointed by the Public Printer to advise on matters pertaining to the Federal Depository Library Program (FDLP) as provided in Title 44 U.S.C. The mission of the DLC is to assist the U.S. Government Printing Office (GPO) in identifying and evaluating alternatives for improving public access to government information through the FDLP and for optimizing available resources. Its 15 members are selected to provide a diverse range of opinion and expertise, and to represent a cross section of the various types of DLP libraries, with at least half of the members employed in depository libraries in positions that provide experience in a documents department. Click here to learn more about the DLC.

depository library number

The unique identification number assigned by the U.S. Government Printing Office (GPO) to each depository library in the Federal Depository Library Program (FDLP), consisting of four digits (example: 0063) or four digits plus an alphabetic character (0063B), used to record the library's selections and to distribute materials. The number can also be used to view an online list of the item numbers selected for receipt by the library (see the Item Lister). The depository library number is included at the beginning of each entry in the online directory of depository libraries available via GPO Acccess (click here to connect). Synonymous with depository number.

depth

The thickness of a bound volume at its thickest point (usually the spine) with the covers included. Average depth determines how many volumes will fit on a shelf of given length. Also refers to the width of a bookshelf from front to back. Most library shelving is 8, 9, 10, or 12 inches deep. See also: height.

In indexing, a combination of the average number of index terms (subject headings or descriptors) assigned to documents indexed and the specificity of the terms used (ASIS Thesaurus of Information Science and Librarianship, Information Today, 1998).

depth curve

See: isobath.

depth indexing

An indexing system that attempts to extract all the concepts covered in a work, including any subtopics, as opposed to summarization, in which a work is indexed only under its dominant subject. Library catalogers have traditionally looked for the single concept that best describes the entire content of an item, leaving depth indexing to commercial services that index parts of items (articles in periodicals, book chapters, essays in collections, etc.).

derivative indexing

A method of indexing in which a human indexer or computer extracts from the title and/or text of a document one or more words or phrases to represent subject(s) of the work, for use as headings under which entries are made. Synonymous with derived indexing and extractive indexing. Compare with assignment indexing. See also: automatic indexing and machine-aided indexing.

derivative work

A work based on one or more preexisting intellectual or creative works, which transforms the content of the original(s) in a significant way. Examples include abridgments, adaptations, musical arrangements, revisions, translations, compilations, etc.). Under U.S. copyright law, the rights to produce derivative works are retained by the copyright holder. Compare with dependent work.

derived cataloging

See: copy cataloging.

derived indexing

See: derivative indexing.

descender

In typography and calligraphy, the stroke of a lowercase letter that extends below the lowest point of an x-height letter (a, c, e, m, etc.). The letters of the roman alphabet that have descenders are: g, j, p, q, and y. The descender line is an imaginary horizontal line connecting the bottoms of descender letters, not to be confused with the base line. Compare with ascender. See also: primary letter.

Describing Archives: A Content Standard (DACS)

Produced by the Canadian-U.S. Task Force on Archival Description (CUSTARD) and funded by the National Endowment for the Humanities (NEH), DACS is a content standard for creating access tools for archival materials, published in 2004 by the Society of American Archivists (SAA). It supersedes Archives, Personal Papers, and Manuscripts (APPM) published by the SAA in 1989. Applicable to all types of archival materials at all levels of description, DACS can be used for any type of descriptive output, including the two most widely used standards, MARC 21 and Encoded Archival Description (EAD). Divided into three parts ("Describing Archival Materials," "Describing Creators," and "Forms of Names"), DACS also includes a glossary, a list of companion standards, and crosswalks to APPM, ISAD(G), ISAAR(CPF), MARC 21, and EAD.

descriptive bibliography

The close study and description of the physical and bibliographic characteristics of books and other materials, including detailed information about author, title, publication history, format, pagination, illustration, printing, binding, appearance, etc., as opposed to an examination of content. Also refers to a work that is the result of such study. Descriptive bibliography is considered a branch of analytical bibliography.

descriptive cataloging

The part of the library cataloging process concerned with identifying and describing the physical and bibliographic characteristics of the item, and with determining the name(s) and title(s) to be used as access points in the catalog, but not with the assignment of subject and form headings. In the United States, Great Britain, and Canada, descriptive cataloging is governed by Anglo-American Cataloguing Rules (AACR2). See also: authority control and subject analysis.

descriptive metadata

Data about an information resource that is intended to facilitate its discovery, identification, and selection. Descriptive metadata is also used to bring together all the versions of a work in a process called collocation, and for acquisition purposes. When viewed as metadata, traditional library cataloging is descriptive, as are such schemes as the Dublin Core Metadata Element Set and the VRA (Visual Resources Association) Core. Descriptive metadata is also used for evaluation, both narrative (reviews, etc.) and formal (content ratings); for linkage (relationships between a resource and other things); and for usability. Compare with administrative metadata and structural metadata.

descriptor

In indexing, a preferred term, notation, or sequence of symbols assigned as an access point in the bibliographic record representing a document to indicate one of the subjects of its text (synonymous in library cataloging with the term subject heading). In bibliographic databases, descriptors appear in the DE or SUBJECT field of the record. Major descriptors are distinguished from minor descriptors by a special character, usually the asterisk. Some abstracting and indexing services, such as ERIC and Psychological Abstracts, provide a list of authorized indexing terms in the form of a printed or online thesaurus. Compare with identifier. See also: aboutness, controlled vocabulary, and descriptor group.

descriptor group

In some indexing systems, preferred terms are grouped in broad subject categories that together serve as a "table of contents" to the controlled vocabulary. The group to which a specific descriptor is assigned is usually indicated by a code in the entry for the term in the thesaurus of indexing terms; for example, the group code GC: 730 in the entry for the term "Literature Reviews" in the Thesaurus of ERIC Descriptors indicates that it is assigned to the descriptor group "Publication/Document Types."

deselection

In serials, the process of identifying subscriptions for cancellation, usually in response to subscription price increases and budgetary constraints. In book and nonprint collections, the process of identifying titles for weeding, usually on the basis of currency, usage, and condition. The opposite of selection.

deselections

Item numbers previously selected by a depository library under the Federal Depository Library Program (FDLP), which it no longer chooses to receive. Deselections can be made at any time in the GPO online database by using the depository library number and a unique password assigned to the library (click here to see the appropriate screen on the FDLP Desktop). Confirmations are sent via e-mail. Amendments appear within two weeks in the Item Lister.

desensitization

The process of deactivating the magnetic strip affixed to a book or other printed item to prevent the security alarm from sounding when the borrower exits the library, a step performed by circulation staff when the item is checked out, using a device called a desensitizer. A different device is required to desensitize magnetic media (audiocassettes, videocassettes, etc.).

desiccant

A drying agent such as silica gel used in museums and libraries to remove water vapor from a small enclosed space when control of relative humidity is an important factor in the preservation of specimens, documents, and other materials in storage or on exhibit. Because desiccants release moisture when heated, they can usually be reused. See also: molecular sieve.

desiderata

A list of books and other materials needed and wanted by a library or archives, to be purchased when budget permits or as cash donations are received. Synonymous in this sense with waiting list and want list. Also refers to a list of subjects or topics on which a writer or researcher requires information.

design drawing

A technical illustration of something conceptualized but not completed, often a line drawing done with more precision than a sketch, intended to provide sufficient detail to allow the object to be fully realized. Executed as part of a design process, design drawing is distinct from art drawing and drafting.

designer binding

A bookbinding bearing decoration done by an artist skilled in graphic design, usually in a style contemporary with the period in which it was made. This type of binding began to appear in trade editions in the second half of the 19th century and remained popular into the early 20th century. Click here to see examples of 19th-century gold-stamped publisher's bindings done in designer-style (Rare Books and Manuscripts Library, Columbia University). For an example of 20th-century book design, see this binding by Paul Bonet (National Art Library, Victoria and Albert Museum). Click here and here and here to see other contemporary examples.

desk copy

A complimentary copy of a new book or recently revised edition provided without charge by the publisher as an instructor's copy when additional copies are ordered by a college or university bookstore for students enrolled in a course of study. An examination copy may become a desk copy once an instructor decides to assign the work as required reading.

desk dictionary

A single-volume dictionary of approximately 150,000 words intended for use by an individual sitting at a desk or in a workspace (example: Webster's New World Dictionary of the American Language). Entries usually indicate orthography, syllabication, pronunciation, etymology, and definition. Synonyms, antonyms, and brief biographical and gazetteer information are included in some editions. Synonymous with college dictionary. Click here to connect to the online version of Merriam-Webster's Collegiate Dictionary and Thesaurus. Compare with pocket dictionary and unabridged dictionary.

desk schedule

A list of the hours during which librarians and other public services staff are regularly assigned to assist users at the circulation desk, reference desk, information desk, or other public service point in a library, usually prepared by the staff member responsible for supervising operations performed at the location. See also: rotation.

desktop binding

Office technologies designed to allow the producer of a multipage document to securely fasten its leaves together, without sending it to a professional binder. An example is VeloBind, an electric punch and strip, hot-knife process often used to custom bind legal documents up to three inches (750 sheets) thick.

desktop computer

See: personal computer.

desktop publishing (DTP)

The use of microcomputer hardware and software for page layout, graphic design, and printing to produce professional-quality camera-ready copy for commercial printing at a fraction of the cost of using the services of a commercial publisher. Used extensively to produce in-house brochures, fliers, newsletters, posters, etc., DTP requires desktop publishing software and a high-speed PC equipped with a large monitor and high-resolution laser printer to produce text and graphics in WYSIWYG format. See also: self-publishing.

destruction

In archives, the process of obliterating records that are no longer of value but remain too sensitive to be simply discarded as trash. For paper records, the most common methods are shredding and pulping. Incineration is used for records in other physical formats. Electronic records may be rendered inaccessible by deletion, an operation that removes the pointer from an index without overwriting the data, but for more sensitive information in electronic format, the data must be overwritten several times or physically destroyed to render recovery impossible.

detached board

A condition in which the front or back board of a book has separated from the rest of the binding, usually along the joint (see this example). The remedy is rebinding. Compare with broken hinge.

detached pages

A condition in which one or more leaves of a bound publication have separated from the book block along the binding edge, a common problem in perfect bindings when the adhesive has dried and cracked (see these examples). A few loose pages can often be tipped in but when entire sections have detached, the remedy is rebinding.

detective fiction

A popular novel, short story, or drama in which the details of a crime (or suspected crime) are uncovered by an amateur or professional sleuth who searches for clues and interprets them, often using ingenious methods to solve the